Table drive for rotary metal forming machines



March 14, 1961 G. H. PERKINS 2,974,707

TABLE DRIVE FOR ROTARY METAL FORMING MACHINES Filed Feb. 10, 1959 5Sheets-Sheet 1 N INVENTOR. M 1!. yxflaw BY 2 S Q ATTORNEY G. H. PERKINS2,974,707

TABLE DRIVE FOR ROTARY METAL FORMING MACHINES March 14, 1961 5Sheets-Sheet 2 Filed Feb. 10, 1959 ill 255::-

HEET

March 14, 1961 G. H. PERKINS 2,974,707

TABLE DRIVE FOR ROTARY METAL FORMING MACHINES Filed Feb. 10, 1959 5Sheets-Sheet 3 4 A TTOENEK March '14, 1961 G. H. PERKINS. 2,974,707

TABLE DRIVE FOR ROTARY METAL FORMING MACHINES Filed Feb. 10, 1959 5Sheets-Sheet 4 INVENT OR.

March 14, 1961 G. H. PERKINS 2,974,707

TABLE DRIVE FOR ROTARY METAL FORMING MACHINES Filed Feb. 10, 1959 5Sheets-Sheet 5 INVENTOR.

A ATTOENEY.

United States Patent TABLE DRIVE FOR ROTARY METAL FORMING George H.Perkins, Euclid, Ohio, assignor to The Cyril Bath Company, Solon, Ohio,a corporation of Ohio Filed Feb. 10, 19s9,ser. No. 792,304 sclaims. cl.153-540 This invention relates tometal forming machines of the typedisclosed inU.S. Letters Patent No. 2,514,830, issued July 11, 1950, toCyril l-Bath, and particularly to anew and improveddrive for therotarydie-supporting table thereof.

'As disclosed in the above entitled patent,'it is a common practice todrive the rotary table of such machines with a ring gear coaxial withthe axis of rotation of the table, and in engagement with, and drivenby, a suitable external pinion gear which, in turn, is driven through aspeed reduction transmission from a conventional source of-motive power.

At the time of the invention'of the machine disclosed inthe abovepatent, the metals customarily drawn were relatively narrow strips, andsmall "diameter'rods and tubes, of ordinary steels, stainless steels,and the like, and of the gauges commonly used in connection withautomobile manufacture. In these particular metals, the elastic limit,yield point, and-ultimate strength are spread a considerable distanceapart so that, 'even though the yield point be exceeded an "appreciableamount tempo-v rarily during stretch forming, there is no danger ofapproaching too closely, or of passing beyond, the ultimate strength ofthe metal and'seriously damaging the crystalline structure or breakingthe work piece. I

At' the same time, since the machines were relatively small compared tothe present machines, the static inertia 2,974,707 Patented Mar. 14,

For example, in present machines, tables which 'themselves weight fourto five tons are not uncommon, and to start such amass and its drivingmechanism without a sudden jerk has become'increasingly difficultand,'.in fact, almost impossible by the means heretofore used;

Consequently, it is apparent that the utility of the machines would becircumscribed considerably unless some means could be provided by whichthis sudden increase in tension, due to the starting jerk of the heavytable and machine, could be overcome, and the starting of the heavytables and the moving parts could be effected gradually and smoothly.The optimum desired, of course, is to start the table with such smallsuccessive increments of movement and applied power that there is nojerk of the table and no sudden increase in the stress on the workpiece.

One problem is to hold the table stationary while applying, by theyieldable tensioning' means, the initial stretch forming force totension the stock to its yield point and then, gradually reducing thistension to a'selected tensioning force below the yield point but abovethe elastic limit, and then to start the table smoothly, without of theparts was low in relation to the stresses necessary for causing damageto, and breakage of,'the workpiece. Accordingly, thetables of suchmachines could be started readily and, though the starting vof thetable'would impose a sudden and rapid increase in the tension appliedafter the stock had been stressed up beyond the elastic limit and to, orclose to, or slightly beyond, the yield point, nevertheless the increasewould not be so great as to endanger the stock seriously or to changegreatly its crystalline structure. However, as the machines have becomeheavier for forming strip and sheet stock of heavier gauges and greaterwidths, and rods and'tubes 'of' gr'ea'ter diameter, the inertialstresses of the machines have increased, and it has become increasinglydifficult, after gradually bringinglthe metal up to the yield point anddropping back below the yield point to a 'selected forming tensionbetween the yield point and elastic limit, prior to starting the table,to maintain the selected forming tension within proper limits as thetable is started and brought up to speed. Invariably, due to the weightofthe table and driving mechanisms and slack in the transmission, thetable starts suddenlywith a jerk and a resultant pull, which the stockis totally inadequate to withstand without'damage. I i Furthermore, atabout the time that'this problem was becoming of some importanceinconnection with the ordinary steels and the like, the high alloymetals were inultimate strength are relatively close'together.

a sudden jerk, and gradually to increase its speed.

The present invention is operative to overcome these difficulties andother problems in connection with formation of stock. Furthermore, thepresent invention contemplates a drive of such a nature that, when usedin combination with wipe and stretch forming machines, the. drivingmeans are engaged with the table in a direc tion generally radially ofthe table and opposite to the direction of thrust of the wipe formingshoe, 'thus, to some extent, counteracting the thrust and balancing thestresses on the table. I

Again, the present invention contemplates a drive by virtue of which apart only of'the drive need be used for light work and the entire drivecan be used for heavy work. In addition, the driving means is such thatone or a number of duplicate drives can be supplied for each machine fordriving the table, depending upon the power required for theiuses towhich the particular machine is to be put, thus providing power meansmore nearly in the proper relation to the majority of the workcontemplated by the customer. This arrangement also makes possible theconversion of a machine originally acquired for lighter work into amachine capable of heavier work,

Various other objects and advantages of the present invention willbecome apparent from the following description wherein reference is madeto the drawings, in which: H

Fig. 1 is a diagrammatic graph illustrating one of the principalproblems in connection with such machines;

Fig. 2 is a top plan view of a combined wipe andstretch forming machineembodying the principles of the present invention, part thereof beingbroken away for clearness in illustration;

Fig. 3 is a front elevation of .the apparatus illustrated in Fig. 2;

' Fig. 4 is a top plan view of the apparatus illustrated in Fig. 2 withthe driving mechanism embodying the principles of the present inventioninstalled; I

Fig. 5 is-a right end elevation of the apparatus illus trated in Fig. 4;I

. Fig.6 is a front elevation of a brake. and clutch mech anism utilizedin the present invention; i Fig. 7 is a right-end elevation of thestructure ll us tratedinFig. 6;, 1 Fig.8 is aperspective view of'aclutch portion of .,the

7o b k a s tchmssha ma Fig. 9'is a fragmentary :view. illustrating theoperation ot/che clutchg-and T .[Q

Fig. is a hydraulic circuit and flow diagram i1lustrating a control forthe present invention.

Referring to Fig. 1, a graph is shown in which the pull exerted on thestock is plotted on the ordinate as against time on the abscissa. Acurve 1 indicates the pull applied to the stock at difierent timesduring the forming operation. Starting at the origin, it is assumed thatthe table is stationary, the stock has been placed under tensionsufficient to determine its yield point and the tension has beendecreased to a selected point between the yield point and the elasticlimit, at which the stock is to be formed. Thus, power has been appliedto the stock by the yieldable stretch forming means for initiallystretching it to its yield point. This power has been reduced to thatdesired for stretch forminga point above the elastic limit.

Thereupon, the table is started at point 2 on the curve. Due to theinertial stresses, the table cannot be started without a sudden jerk,particularly inasmuch as tension is being applied to the stock tendingto rotate the table in the direction opposite to that in which it is tobe rotated for stretch forming. Accordingly, this sudden jerk applied onthe stock causes an abrupt rise in the pull exerted on the stock, sothat the curve rises rapidly to a point indicated at 3. By this time,the static inertia of the table has been overcome and the continuedapplication of power maintains the table at the proper speed. The suddenjerk imposed by the starting of the table does not continue but dropsoff rapidly to a point indicated at 4, at which point the table hassteadied down to the proper forming speed, and thereafter the pull ismaintained substantially steady during the remainder of the operation,or, if increased or decreased to adjust to changes in configuration ofthe die and the like, the increase or decrease is gradual. These changesin latter tension are predetermined and gradually applied and can beallowed for, and are not sudden changes.

Specifically, therefore, it may be said that one of the principalobjects of the present invention is to so apply power to the table thatthe parts of the curve between points 2 and 3, and 3 and 4, areeliminated and, instead, the curve passes smoothly from the point 210the point 4 without any appreciable change. Thus, the stress applied tothe stock throughout the entire forming operation does not exceed thepredetermined pull that is desired.

Referring therefore to the specific apparatus for carrying out thisprocedure, a combined wipe and stretch forming machine, such asillustrated in the above entitled identified patent, is shown forpurposes of illustration. The machine comprises a frame 10 having a mainportion 10a on which is mounted a stretch forming piston and cylinderassemblage and a lateral portion 10b on which is mounted a wipe formingpiston and cylinder assemblage, so that the stock can be subjectedeither to wipe forming or stretch forming, or to both concurrently.

Mounted on the frame 10 for rotation about an upright axis or post 11 isa rotary table 12 on which is mounted a side face die 13. A suitableclamp 14 is provided on the table for securing one end of a length ofstock S to be formed in fixed position relative to the die.

For stretch forming the stock, a stretch forming piston and cylinderassemblage 15 is provided on the frame main portion 10a. As described ingreater detail in the above entitled patent, this stretch formingassemblage comprises a cylinder 16 in which is reciprocably mountedincluding the slide 19, is mounted on .a carriage 23 which is rotatableabout an upright pivot 24 so that the assemblage can align itselfproperly with the point of tangency between the stock and the side facedie during stretch forming.

Mounted on the frame portion 10b is a wipe forming piston and cylinderassemblage 30 comprising a cylinder 31 with a piston 32 reciprocabletherein and having a rod 33 connected to :a pedestal 34 of a slide 35.The slide 35 is mounted in a slideway 36 for movement in a directionparallel to the axis of the piston and cylinder assemblage 30. Asuitable wipe forming shoe 37 is mounted on the pedestal 34.

In order to drive the table 12 in opposite directions about its axis, asdesired, the table is provided with a ring gear 38 coaxial with thebearing post 11.

The structure thus far described is fully disclosed in the aboveentitled Patent No. 2,514,830.

In accordance with the present invention, the ring gear 38 is in meshwith a plurality of pinion gears 40 which are distributedcircurnferentially of the table 12. In the form illustrated, two suchgears 40 are used, though more may be used, depending upon the torque.to .be applied to the table. The gears 40 are positioned across thetable fromthe wipe forming assemblage 30 ,so that the thrust of thatassemblage against the die tending to tilt the table toward the gearsWis-resisted by the gears, and the .stresses imposed by the two are tosome [extent balanced and better distributed. The two gears 40 shown arearranged at opposite sides of a plane through the axis of the table andthe axis of the assemblage 30 in the normal centered operating positionof the assemblage 30, the gears 40 being placed about 37 to each side ofsuch plane.

It is desirable that the driving mechanism of each gear 40 be identicalwith that of each other gear 40, and that each one of the drivingmechanisms be such that it can provide adequate power .to drive thetable for the light forming requirements of the .machine. Thus, toprovide :a machine of increased tonnage from one of light tonnage, up tothe full .capacity of which its physical structure is capable, all thatis necessary is to add additional identical driving mechanisms anddistribute them circum-ferentially of the machine.

Pressure fluid for operating the piston and cylinder assemblages issupplied from a suitable pump 41 driven by an electric motor 42, whichmay be the motor which drives a pump forsupplying pressure fluid foroperating the gears 40.

The assemblage 15 is connected to the pressure source supplied by thepump through a suitable control valve 43, and the assemblage 30correspondingly is connected through a suitable valve 44, these valvesbeing the customary valves by which pressure fluid can be supplied toeither end-of the associated assemblage ,and the opposite end ventedconcurrently, and, by which, when desired, both ends can be vented orblocked, concurrently, in accordance with the desires of the customer.The specific manipulations of the piston and cylinders for the formingoperation are ,fully set forth in the above entitled patent and form nopart of the present invention.

As mentioned, the tables in machines of this type have reached largesizes, four to five tons and largerbeing not uncommon. Likewise, thesetables are of large diameter. Since they are designed to form variouslarge sheets of metal and subject it to extremely high forces, theyare'usually driven at comparatively slow speeds. and, for economicaldrive, are driven through reduced speed transmissions in which the speedreduction from the driving motor to the table may be reduced to as muchas one revolution of the table .to 4.3100 revolutions, or more, of themotor.

Each driving mechanism, as best illustrated in Figs. 4 and 5, comprisesa speed reduction power'transmission 45 which may be o'fthe--conventional reduction 'geartypc.

The transmission 45 has a driving shaft 46, one end of which, indicatedat 46a, extends out of the one side of the transmission housingand theother end of which, indicated at 46b, extends out of the opposite side.The transmission has an output shaft 47 which is drivingly connected toa worm gear 48 to which, in turn, is drivingly connected a pinion gear49 keyed to a shaft 50 to which the gear 40 is also keyed incoaxialrelation. Thus the drive of the table is through the speedreduction transmission 45, and if the shaft 46 is turning 4300revolutions per minute,- the speed of the gear 40 is such that the table12 is turned one revolution per minute. The transmission 45 is driven bya. pair of. hydraulic motors the line 56, and, again, both of them areresponsive t6 the valve 58.

Mounted on the shaft 46 is a tachometer 64 which supplies electricsignals in accordance with the speed of the motors 51 and 52 through anamplifier 65 to a signal responsive control 66 on the pump 54, thuschanging the volumetric delivery of the pump in accordance with thetachometer reading. This control is of a well known type which canreadily be set so that, if the speed signal indicated -by the tachometervaries appreciably from that preselected, the volumetric discharge ofthe'pump 54 will be varied accordingly so as to increase or decrease 51and 52 which are connected in coaxial relation on the same shaftextension 46a.

As herein more fully set forth, the hydraulic circuit leading from thepump to the motors is such that the motors can be connected in parallel,or one of the motors can be used alone, thus providing'motive power morein keeping with extremely heavy forming operations and relatively lightforming operations, respectively. Fluid pressure is supplied to themotors, as will be more fully described hereinafter.

At this point, it should be noted that there is' another distinctiveadvantage in having a plurality of the identical driving mechanisms, andhaving a plurality of identical motors for driving each mechanism. Theinertial stresses due to the starting of the table are not merely due tothe weight of the table itself but are augmented by the additionalweight of all of the driving parts back to,-and including, the hydraulicmotors 51 and 52. Thus the inertial forces to be overcome are reduced ifonly one of the driving mechanisms is employed, whereas it is increasedifa number are employed. Furthermore, if only one mechanism is employed,inertial forces are further reduced if only one motor of the mechanismis employed. All of these factors enter into providing a power source inkeeping with the operation and in providing smoother operation.Obviously, the less .the inertial forces, the less is the danger ofcausing a sudden jerk in the table, and the morenearly can the optimumof starting the table with almost microscopic increments in the speed ofrotation and in applied power, both of which gradually increase untilthe proper power and table speed, be obtained. It is desired that thehydraulic motors operate, however, at the proper speed and, for thispurpose, suitable controls may be, provided. As illustrated, the powersupplied to the motors is from a variable volumetric delivery hydraulicpump 54 driven by an electric motor 55. The preselected pressure fluidsupplied by the pump is delivered to the main lines 56 and 57 through asuitable reversing valve 58. A suitable supplementary pump 59 may beprovided for maintaining v the system loaded with pressure fluid duringperiods when it is inoperative or idling. The pressure fluid isconducted from the lines 56 and 57 to suitable control valves 61arranged one control valve for each one of the driving mechanisms. Sincethe driving units are the same in form and function, one only will bedescribed.

Each valve 61 is arranged to connect its associated motors 51 and 52hydraulically in parallel with each other, or to connect the motor 52 tothe source and the motor 51 for idling. In the form illustrated, thevalve 61 has a plug 62 which normally is in the position shown, the plugportion 62a being operative. The plug portion 62a, when in the positionillustrated, blocks the lines 56 and 57 at a point between the motor 51and pump 54 and beyond the leads to the motor 52. At the same time, itconnects the input and discharge of'the motor 51 together so that themotor 51 can idle. Thus, only the motor 52 is operable in response tovalve 58. When, however, the plug 62 is shifted so that the portions 62bbecome operative, then both of-the motors 51 and. 52 are connected inparallel to the'pressure' line 57 and to the pump delivery, and'bringthe'motors 51 and 52 to the proper speed. The pressure of the deliveredfluid is preselected and set by a pressure control valve 67 which may,if desired, be set to different values during stretch forming ifdictated by the requirements of the partic: ular piece being formed.

Since it isdesirable to operate the apparatus from a central controlpanel, the valve 61 may be operated by a suitable solenoid, such asindicated at 68, and the valve 58 may be operated by a suitable solenoidsuch as indicated at 69.

As mentioned, it is desirable to preload all of thedriving mechanismsincluding the motors 51 and 52, the speed reduction transmission 45, themechanism connected between it and the gear 40, the gear 40, the'ringgear 38, and table 12. This can be accomplished by supplying pressure.flu idto the motors 51 and 52 in a quantity sufiicient to drive them inthe selected table driving direction sufliciently torotate the tableslightly. Since reduction is 4300 motor revolutions to one tablerevolution, the motors can operate slowly to drive without moving thetable appreciably. Thus slack is eliminated and static inertia ispartially overcome. Accordingly, the startingof the table can be'efiected by gradually increasing the delivery of the variable deliverypump 54. While this pressure is being maintained and the table either iscreeping by negligible increments, or is merely subject to slight torquesufiicient only' to balance the friction, the stock is connected at oneend to the clamp 14 'and'at the other end to the stretch forming head21. In this condition, pressure is admitted to the rod end of thestretch forming piston and cylinder assemblage 15,

for applying tension on the stock to bring the-stock up to its yieldpoint. However, when this pressure is applied, the resulting tension onthe stock tends to rotate the table in a direction opposite to that inwhich it is rotated by the motors 51 and 52. For example, in Fig. 2, thedrive to be maintained for the particular stretching operation is suchas to urge the table in a counterclockwise direction, whereas thetension on the stock is such as to urge the table in a clockwisedirection.

.At this point, it should be noted that the power adequate onlytomaintain the table rotating by negligible increments so that it ispractically static but with all the slack eliminated in its drive andwith its static inertia overcome, all the way from the motors through tothe ring gear 38, is insuflicient to hold the table against the pullexerted through the stock by the assemblage 15. If, before applyingtension by the assemblage 15, the table driving power were increased towithstand its contemplated pull, then the table would be rotated at anappreciable speed and the stock would be subject to a severe jerk as theassemblage 15 became efiective or slack in the stock were eliminated. Itis necessary, therefore, that the drive to the table be arranged sothat, while the table and its driving mechanism has no, or only aslight, forward rotation free from slack, it has'a braking resistance torotation in theopposite direction by the tension applied to the stockgreater than will be applied by the assemblage 15. For this purpose, aone-way braking clutch deviceisused. Referring to the Figs. 2 through 9,the braking clutch device, indicated at 70, .is connected to the speedreduction transmission 45, preferably on the input shaft extension 46bof the transmission. It is to be noted that two one-way braking devicesare provided and these operate in opposite directions, respectively, thepurpose being that onedevice can operate when the table is driven in onedirection and the other when the table is driven in the oppositedirection, the table drive, of course, being reversed by the reversal ofthe motors 51 and 52. In each case, the one of the devices which is notfunctioning for its intended purpose is idling. Each of the devicescomprises one member driven by the extension shaft 46b and anothermember which is secured fixedly to the frame of the machine or housingof the transmission 45. In the form illustrated, each device has a drum71 which is fixedly connected to the shaft 46b, and an .outer drum 72which, as will later be described, can rotate in one direction with thedrum 71 but is prevented from rotation in the opposite directionrelative thereto. The drum 72, in turn, is engaged by brake shoes 73pivotally mounted on a frame 74 of the transmission and which can beoperated to arrest rotation of the drum 72 and release the drum 72,respectively. The brake shoes 73 are released by a suitable solenoid 75and applied by a spring 76. A suitable adjusting screw is provided foradjusting the tension of the spring 76 so as to control the shoeapplying power.

Interposed between the drums 71 and 72 are a plurality of .cams 80.These cams are arranged so that when the shaft or drum 71 is driven inone direction, they interlock the drum 71 and the drum 72. When the 71is driven in the opposite direction, they release the drum 71 from thedrum 72.

As best illustrated in Figs. 6 and 7, for example, if the drum 72 isconstrained from rotation by the brake shoes 73, and the drum 71 isdriven as indicated by the arrow 81, for driving the table 12 in thestretching direction, then the cams 80 rock so that their peaks 82 arereleased from the drum 72, in which case the drum 71 and the shaft 46can turn unrestrained and drive the table for stretching. On the otherhand, if the pull on the table by the assemblage 15, through the stock,is such as to tend to reverse the direction of rotation of the table 12,and thereby the rotation of the shaft 46, .then the drum 71 would beturned in a clockwise direction, and if the drum 72 is then held by thebrake shoe 73, the cams 80 are rocked, as indicated by the arrows 83, soas to wedge the peak 82 firmly against the drum 72 and lock the drumstogether. Thus, the brake mechanism 70 is operative through the drum 72to permit the drum 71, and therefore the shaft 46, to turn freely in thetable driving direction and to prevent its return in the oppositedirection. This amounts, in effect, to a ratchet connection whichpermits the shaft 46 to turn in the proper direction for driving thetable against the pull exerted by the stretch forming assemblage, butwhich locks to prevent the return in the opposite direction, the teethof such a ratchet being, in fact, infinitely small, .since the relativecircumferential displacement of the drums 71 and 72 is so slight foreifecting the .wedging and releasing action of the cams 80 that it mightbe said to be instantaneous. For example, the trelativerotation of thedrums .through a circumferential distance of a .very small fraction ofan inch is all that is necessary to move the cams from released positioninto firm locking position, thus the ,drum 71 and the shaft 46 may turnfreelyinone direction hut, upon avery, very slight movement in theopposite direction,-they are latched. Since thisslight movement ,must bereflected to the table through a reduction gearing which supplies areduction in the neighborhood of 4300 to 1, the slight relative rotationof the two drums for causing the release andengagement of the cams 80 isnot reflected in any noticeable or measureable movementpn the table,being, for example, one forty-.threehundredthof one sixteenth of aninchat the most. If only one one-way clutch 8 reversible drive, then thebrake is not essential, but, instead the drum 72 is permanently securedto the frame 74 in a non-rotative position.

The two. clutches of each driving mechanism are arranged so that eachoperates in an opposite direction to the other, as mentioned, so thatthe shaft is free to drive the table in one direction and prevent itsreturn in the opposite direction by virtue of locking of one of thedrums 72 and releasing of the other. Therefore, the brakes are provided.The clutches preferably are located on the inp t shaft of thetransmission so that the torque to which they are subjected isrelatively small compared to the torque applied to the table 12. If itis desired to reverse the'entire driving mechanism, the drum 72originally looked is released by its brake and the opposite drum 72 ofthe same driving mechanism is latched by its brake. Thereafter theclutch works, in its driving cycle, in the proper direction for latchingthe table against rotation bythe application of stretch forming tensionby the piston and cylinder assemblage 15, and, at the same time, forpreloading and very slightly rotating the table by the driving mechanismso that there is no objectional jerk on the stock due to the starting ofthe table, the jerk being so very minute so as to be negligible so faras the present metals such as the high titanium alloys and the like areconcerned. By increasing the number of driving mechanisms, smoothness ofoperation can be increased for higher power machines, but ordinarily twoor three drive mechanisms are suflicient.

Referring to Fig. l, the dotted line joining the points 2 and 4indicates that there is a very slight, almost imperceptible, increase intension on the stock due to the starting of the table 12. However, sincethe table is already preloaded and ready to move, or is moving,

is required, as when the table is not equipped with a 1" there is nojerk due to the inertia of the parts but the table starts slowly and itsspeed gradually increases by minute increments to that for which thevolumetric delivery of the pump is set, as determined by the tachometers64. Accordingly, with the present invention, the parts in which highinertial stresses arise are reduced to a minimum for the particular jobby virtue of using only the number of individual drive mechanismsrequired for the forces involved. Thus, the inertial stresses can bereduced to the point where one driving mechanism with one motor thereofsupplies the power. Thereby, the power applied and the inertial stressesdue to that power can he proportioned more nearly to the power that isnecessary for the stretch forming operation. Furthermore, due to thepositioning of the individual units about the axis of the table, heavyforces imposed by the wipe forming assemblage can be to some extentequalized and counterbalance so that the overall stresses imposed on thetable and tending to tilt it are better distributed. This becomesimportant with the large sheets of the higher alloys in which thestresses imposed on the table by the wipe forming assemblage areextremely great.

Furthermore, by virtue of the one-way clutches and brakes, operation ofthe table can be obtained in either direction and the table preloaded sothat the initial stretch forming tension can be applied without rotatingthe table, opposite to the forming direction, and 'the table can bestarted forwardly without a sudden jerk, all of the slack having beeneliminated prior thereto and a substantial pressure built onthe table,Whichcan thereby then be increased gradually and smoothly by smallincrements.

The words horizontal, vertical, horizontally, and vertically-' and thelike, are used in the description and claims for convenience indescribing the relative positions of theparts and not as absolutes,inasmuch as the invention has been illustrated as used with a machine inwhich a turntable is arranged with its axis extending vertically.Obviously, theentire machine can be disposed so that the axis of theturntable is other than vertical so long as the relative positions ofthe parts are maintained.

Having thus described my invention, I claim:

1. In a stretch forming machine, a frame, a turntable mounted on theframe for rotation about an upright axis and adapted to support a sideface die, means rotatable with the table and adapted for clamping oneend of the stock for holding the clamped end in fixed position relativeto the die, a stretch forming assemblage on the frame and connectable tothe opposite end of the stock for applying yieldable stretch formingtension thereto, driving means connected to the table, said drivingmeans including a rotatable power transmission shaft drivingly connectedto the table and operative, when rotatably driven in one direction, todrive the table in a stretching direction for stretching the stock, aoneway braking device including one member connected to the shaft forrotation by, and in fixed relation to, the shaft, a braking member,means interposed between the members and rendered operative by slightinitial rotation of said one member by the shaft, when the shaft isrotated in a direction opposite to said one direction by rotation of thetable opposite to the stretching direction, for locking the memberstogether to prevent rotation of the table opposite to the stretchingdirection, and rendered operative by rotation of said one member by theshaft, when the shaft is rotated in said one direction, for releasingsaid one member for rotation relative to the braking member so that theshaft can rotate unrest-rained and drive the table in said stretchingdirection.

2. The structure according to claim 1 wherein said braking member isnormally rotatable in said opposite directions, and the braking deviceincludes a braking means which is operable to constrain the brakingmember from rotation and to release it for rotation, selectively.

3. The structure according to claim 2 characterized in that at least twoof said one-way braking devices are dr-ivingly connected to ,said shaft,one being operable in one direction and releasable in the oppositedirection, and the other, being operable in said opposite direction andreleasable in said one direction, and means to render said devicesoperable and inoperable, selectively.

References Cited in the file of this patent UNITED STATES PATENTS2,514,830 Bath July ll, 1950 2,514,831 Bath July 11, 1950

